My U.S. Pat. No. 5,884,899 entitled "HalfProfile Gate Valve ," discloses an improved gate valve with a low-profile design for economy of size, as discussed therein. This reference is incorporated herein. The gate valve of my '899 patent is designed for "opened" and "closed" positions to allow for either full flow or no flow of gaseous fluids through the valve. The present invention improves upon the design of my '899 patent gate valve by providing therewith a throttling valve to provide for variable gas flow in order to precisely control the operating parameters, such as pressure and temperature, within a process chamber.
Throttling butterfly valves and vacuum pressure control throttling multi-vane valves are also known in the art and are commonly used for controlling process variables. Butterfly valve have the advantage of being relatively simple in design, which reduces their cost and maintenance, but they have limited ability to achieve a linear conductance response. Multi-vane throttle valves, such as the Vari-Q Throttle Valve sold by MeiVac, Inc. of San Jose, Calif., USA, provide more precise control than butterfly valves, but are much more complicated in design. Thus, a need exists for a simple throttle valve design that achieves more linear conductance response.